Prognostic significance of LAPTM4B and p27kiP1 expression in triple-negative breast cancer

BACKGROUD: Triple-negative breast cancer (TNBC) is associated with an aggressive phenotype and poor prognosis, and the lack of druggable markers leads to the unavailability of targeted therapies. Thus, there is an urgent need to identify potential targets for triple-negative breast cancer. OBJECTIVE: In this study, we aimed to explore the expression of LAPTM4B and p27(kiP1) in triple-negative breast cancer, and its clinical significance. METHODS: We analyzed the expression and association of LAPTM4B and p27(kip)(1) in human breast cancer databases. To analyze the role of LAPTM4B in the aggressiveness of the human triple-negative breast cancer, the expressions of LAPTM4B were knocked down in MDA-MB-231 and HCC1187 cell lines. Then, cell proliferation, migration and apoptosis were assessed in vitro. Furthermore, the immunohistochemistry examinations of LAPTM4B and p27(kip)(1) expression were performed using surgical specimens from 188 primary triple-negative breast cancer patients. RESULTS: Through analyses of several independent breast cancer cohorts,. we found the correlation of the LAPTM4B and p27(kip)(1) expression. Remarkably, the knockdown of LAPTM4B restored p27(kiP1) expression and inhibited the aggressiveness of breast cancer cells. Meanwhile, the knockdown of p27(kip)(1) relieved the suppression of cell migration. Consistent with the analyses of human breast cancer cohorts, the immunohistochemistry results showed that the expression levels of LAPTM4B and p27(kip1) were correlated in 188 triple-negative breast cancer samples (p = 0.019). We also validated that the higher LAPTM4B expression, the lower p27(kip)(1) expression (p = 0.0001), and the LAPTM4B-f/p27(kiP1)- subgroup (p < 0.0001) were poor prognostic indicators, as well as the higher histologic grade (p = 0.0001). In the multivariate Cox regression, p27(kip)(1) expression was considered as an independent predictor of survival (p < 0.001). CONCLUSIONS: The overexpression of LAPTM4B and the loss of p27(kiP1) expression are correlated. Meanwhile, the up-regulated expression of LAPTM4B together with the down-regulated expression of p27(kiP1) could classified a group of breast cancer patients with poor prognosis, consequently considered as a potentially prognostic marker and candidate target for therapeutic intervention of triple-negative breast cancer.